A lock device has conventionally been provided on door panels together with a door lock mechanism in vehicles such as automobiles, for example. The same lock devices have also been provided in a steering column, a fuel filler opening and the like of the vehicles. A single key is co-used for these lock devices in the vehicles as well known in the art.
Differing from reversible keys, the key of the above-described type sometimes has opposite edges of a key body or shank formed into asymmetric shapes as described above. When locking and unlocking are carried out with the asymmetric key, a user needs to insert the key into a key-insertion hole of the lock device with a correct orientation. More specifically, when the key is inserted with an incorrect orientation and forced to be turned in a half inserted state, there is a possibility that the key may be deformed or broken, or the rotor side of the lock device may be broken, for example. (See Patent Document 1 regarding the reversible keys and asymmetric keys.)